How to tell if tubes are matched?

Relax. This is not a new problem. Normally only output (large) tubes are matched. If input (small) tubes are not marked "left" and "right" etc., it won't matter. The output tubes will be marked as pairs in some fashion. Before you rip the boxes open, look for rubber bands holding pairs (or quads) together. Alternatively, the boxes themselves will be marked. I store my tube boxes in the exact same order that the tubes are installed in my amps, so if I try another set ,the tubes always go back in the original boxes. Stay cool, and if when your amp arrives you are not certain, post again with specifics, and somebody will walk you through it.
Do make certain that you plug the small input tubes in the correct sockets, if you get them backwards (i.e. put the 12ax7 in the socket intended for the 12at7, the darn thing might not work. Read the instructions concerning output tube bias carefully before you proceed. Tubes are tough and will withstand abuse, but improper bias will kill them off in a hurry.
Finally, tubes have been around for almost a century. If they were difficult and delicate flowers, they would have been abandoned long ago.

If the output tubes are way off, you might have problem adjusting their bias. But in general, there is no way to tell if the two tubes are matched without running them through test equipment.

Just a follow up. Some Amp manufactures will hand write the matched pair #s and socket# on the tubes with a marker.In any case they are marked in some fashion. This is because they have also set the bias voltage for the power tubes.

Jim

If your serious get a tube tester from Ebay. We matched gain on 12AX7's for our Jolida hybrid and found it to be WELL worth while. If you have 6L6's or KT88's in the final - you will find a good used tube checker a valuable tool. We matched tubes for our older Conrad Johnson PremierII - also could hear the difference.

I don't wish to be difficult, but getting a tube checker is not a good short range idea. The old (and I do mean old) tube checkers that are most often for sale, are only useful to separate the living from the dead (and many fail this criterion). Suggestions to the contrary are misinformed.

1. tube checkers must be calibrated to be of much use in matching
2. tube matching is not an easy or quick art to learn
3. power tube matching requires more than simple transconductance matching, it requires proper loading as well, a facility few, if any, commercial units have. A match of 5% under a realistic load is the usual standard.